It is widely recognized that plaques or lesions within body vasculature may be classified into three broad categories, viz., calcified or hard, fibrous, or inflamed lipid filled plaque. The detection and identification of inflamed plaques is important since such lesions are at the greatest risk of rupture, resulting in a large thrombus or blood clot to form and occlude the flow of blood through the artery, thereby causing irreversible injury to the heart or brain.
An inflamed or vulnerable plaque may be characterized by its cap thickness, lipid pool size, and the pondus Hydrogenii (pH) of the blood in its vicinity. In general, the pH of the blood in the vicinity, or at an immediately distal location, of such lesions may be somewhat lower than normal. Additionally, the region of an inflamed plaque is relatively warmer than the surrounding tissue. Numerous devices such as fiber optic systems with infra-red detectors have been proposed, however, such devices are very expensive, making them available only in a limited number of procedures. Therefore, there is a need for a relatively inexpensive means of detecting vulnerable plaque within the blood vessel.